Cleaning mechanism for photoconductive surfaces

ABSTRACT

A cleaning system for the moving photoconductive surface of an image transfer electrostatic copying system using a developer made up of toner particles and a liquid carrier in which a cleaning belt with a rough surface is constrained to cause an area of the belt surface to contact the photoconductive surface at a location past the image transfer station with the belt being driven in a direction opposite to the direction of movement of the photoconductive surface and with clear carrier liquid being metered across the photoconductive surface just ahead of the cleaning belt at a rate which is approximately equal to the rate at which the carrier liquid evaporates from the developer. Preferably the belt is reciprocated transversely and preferably the photoconductive surface is flooded with light as it leaves the image transfer station.

United States Patent [1 1 Smith et al.

[ Dec.4, 1973 [75] Inventors: Ian E. Smith, Lockleys; Peter J.

Hastwell, Elizabeth Grove; Marinus C. Vermeulen, Valley View, all ofAustralia v [73] Assignee: Savin Business Machines Corporation,Valhalla, NY.

[22] Filed: Feb. 24, 1972 [21] Appl. No.: 228,873

[52] US. Cl 355/15, 117/37 LE, 355/10 [51] Int. Cl. G03g 15/00 [58]Field of Search 355/15, 10; 117/37 LE; l5/256.53

[56] 7 References Cited UNITED STATES PATENTS 3,711,796 1/1973 Saito .7355/15 I 3,656,948 4/1972 Mammino 355/15 X 3,276,896 10/1966 Fisher117/37 LE 3,576,624 4/ 1971 Matkan 117/37 LE 3,526,457 9/1970 Diamond etal. 355/ 15 2,728,103 12/1955 Benedict e't l5/256.53 X

3,405,683 10/1968 Jons et al 117/37 LE 3,622,237 11/1971 Vongrabe 355/153,318,212 5/1967 Rubin 355/3 CLEANING MECHANISM FOR PHOTOCONDUCTIVESURFACES 3/1972 Amidon et 51., 117/37 LE OTHER PUBLICATIONS PrimaryExaminer-Richard L. Moses Attorneyl-1enry L. Shenier et al.

[5 7] ABSTRACT A cleaning system for the moving photoconductive surfaceof an image transfer electrostatic copying system using a developer madeup of toner particles and a liquid carrier in which a cleaning belt witha rough surface is constrained to cause an area of the belt surface tocontact the photoconductive surface at a location past the imagetransfer station with the belt being driven in a direction opposite tothe direction of movement of the photoconductive surface and with clearcarrier liquid being metered across the photoconductive surface justahead of the cleaning belt at a rate which is approximately equal to therate at which the carrier liquid evaporates from the developer.Preferably the belt is reciprocated transversely and preferably thephotoconductive surface is flooded with light as it leaves the imagetransfer station.

18 Claims, 10 Drawing Figures PATENTED DEC 75 SHEET 1 0F 5 PATENTEU B41975 SHEEI 2 OF 5 M W HM WH wmmwm E Hm 'lllllllll-llllllll II II II IIII II l l I I .ll lllIIIllIll.

CLEANING MECHANISM FOR PHOTOCONDUCTIYE SURFACES BACKGROUND OF THEINVENTION 155,108, filed June 21, 1971, discloses a Method of ContactTransfer of Developed Electrostatic Images and Means for Practicing theSame. In the arrangement disclosed in our copending application, aphotoconductive surface is moved successively past a charging stationand an exposure station and a developing station and an image transferstation. In the course of its operation, the surface first receives astatic charge and then is exposed to the image to be copied to produce alatent electrostatic image on the surface. In our copending application,the latent image is developed by subjecting the surface to the action ofa developer comprising particles of a tacky toner in a suitable carrier.Following this development of the image, the surface is brought intointimate contact with the material on which the copy is to be made.Owing to the greater affinity of the tacky toner for the copy material,such as paper, than for thephotoconductive surface, the image istransferred to the copy material.

Ideally, in the operation of a machine such as that described above, allof the toner particles would be transferred from the photoconductivesurface to the copy material in the course of the image transferringstep. Such, however, is not the case, and some toner particles remainadhered to the photoconductive surface. It will readily be appreciatedthat after a relatively short period of time in use, the surface willbecome so dirty that copies made by the machine are entirelyunsatisfactory. This may be the result of interference by the buildupwith the charging operation and the exposure operation or haphazardtransfer of some of the buildup during subsequent copying operations.

fectively cleans the photoconductive surface of an image transferelectrophotographic system. Our mechanism requires maintenance at onlyrelatively infrequent intervals. It has a long life in use. It is simplein construction and in operation for the results achieved thereby.

SUMMARY or THE INVENTION One object of our invention is to provide acleaning mechanism for the photoconductive surface of an image transferelectrostatic copying machine.

Another object of our invention is to provide a cleaning mechanism whicheffectively cleans a photoconductive surface of toner particles adheredthereto.

A further object of our invention is to provide a cleaning mechanism forphotoconductive surfaces which does not require frequent maintenance.

Still another object of our invention is to provide a cleaning mechanismfor a photoconductive surface which is simple in construction and inoperation for the result achieved thereby.

- Other and further objects of our invention will appear from thefollowing description.

In general our invention contemplates the provision of a cleaningmechanism for the moving photoconductive surface of an image transferelectrostatic copying machine using liquid developer comprising tonerparticles in a carrier in which an area of the rough surface of acleaning belt driven in a direction opposite to the movement of the drumsurface, engages the drum surface at a location past the image transferstation and in which developer liquid is metered into the surface justahead of the belt at a rate substantially equal to the rate at whichliquid evaporates from the developer system of the machine. Preferably,we flood the surface with light as it leaves the transfer station tofacilitate the cleaning operation. Further the belt may be reciprocatedtransversely as it is driven to enhance the scrubbing action thereof.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings whichform part of the instant specification and which are to be read inconjunction therewith and in which like reference numerals are used toindicate like parts in the various views:

FIG. 1 is a schematic view of an image transfer electrostatic copyingmachine incorporating one form of our cleaning mechanism.

FIG. 2 is a sectional view of the form of our cleaning mechanism forphotoconductive surfaces illustrated in FIG. 1.

FIG. 3 is a top plan view of the form of our cleaning mechanismillustrated in FIG. 2 taken along the line 3-3 of FIG. 2.

FIG. 4 is an end elevation of the form of our cleaning mechanism shownin FIG. 2 taken along the line 4-4 of FIG. 2.

FIG. 5 is an end elevation of the mechanism illustrated in FIG. 3 takenalong the line 5-5 of FIG. 3.

FIG. 6 is a fragmentary sectional view of one form of cleaning beltwhich we may employ in our system.

FIG. 7 is a fragmentary perspective view of the liquid metering portionof our cleaning mechanism for photoconductive surfaces.

FIG; 8 is a sectional view of the liquid supply pump of our cleaningmechanism for photoconductive surfaces.

FIG. 9 is a perspective view of an alternate form of our cleaningmechanism for photoconductive surfaces.

FIG. 10 is a fragmentary sectional view of the form of our cleaningmechanism illustrated in FIG. 9 showing an alternate arrangement of thedoctor blade thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, oneform of image transfer electrophotographic copying apparatus, indicatedgenerally by the reference character 10, with which our cleaning systemcan be used, includes a drum 12, having a photoconductive surface 14.Drum 12 is supported on a shaft 16 adapted to be driven in any suitablemanner in the direction of the arrow in FIG. 1 to carry thephotoconductive surface past an exhaust discharge lamp 18, a chargingstation at which a corona 20 applies a charge to the surface, past anexposure station at which the machine optics 22 expose the surface to animage of the material to be copied and to a developing station at whicha tray 24 carrying developer liquid is located. As the latent imagepasses through the tray 24, it is subjected to the action of aliquiddeveloper comprising toner particles in a liquid carrier. In thearrangement shown in our copending application in the course of thedevelopment of the image, tacky toner particles adhere to areas of thesurface 14 which retain the charge, thus to develop the image.

As the surface 14 carrying the developed image leaves the developertank, it is subjected to light from a lamp 26 which is adapted to bleedany background charge off the surface. Next, the image travels through atransfer region at which the image is transferred to the surface ofsuitable copy material, such as paper 28, which is fed from a supplyroll 30-and through a heater 32 around guide rolls 34 and 36 intocontact with the drum. As the paper and the drum surface move togetherthe toner particles making up the developed image are transferred to thepaper until the paper arrives at a pair of rolls 38 and 40 which deliverthe copy to the user of the machine. It will readily be appreciated thata suitable cutter (not shown) may be incorporated in the machine to cutthe copy to length.

A first pump 42 is adapted to supply developer liquid to the tray 24through a line 44. Overflow from the tray 24 is collected in a trough 46from whence the developer flows through a line 48 and through a tonerconcentrate sensing arrangement 50 to a supply tank 52. A line 54connects the tank 52 to the intake of pump 42.

A second pump 56 connected to tank 52 by a line 58 feeds developer fromthe tank to a line 60 leading into an impingement mill indicatedgenerally by the reference character 62 which feeds developer to tank 52through a line 64. In response to a signal from the sensing system 50,additional concentrate is fed to the mill 62 from a supply tank 66through a pipe 68. The developer supply apparatus including mill 62 isdescribed in greater detail in our copending application Ser. No.212,155 filed Dec. 27, 1971. Our system differs from that disclosed inthe last-mentioned application only in that, for a reason which will beapparent from the following description, clear carrier liquid is notsupplied directly to the mill 62. One carrier liquid or diluent which wemay use is an isomerized paraffinic hydrocarbon having a specificgravity of 0.75 at 60F. and a kauri-butanol number of 27. This materialis manufactured by Standard Oil Company of New Jersey and sold under thetrademark ISOPAR G. Other diluents and examples of toners we may employare disclosed in our firstmentioned copending application.

. We'position our cleaning mechanism, indicated generally by thereference character 70, at a location around the periphery of the drum12 between copy discharge rolls 38 and 40 and the exhaust exposure lamp18.

Referring now to FIGS. 2 to 5, the form of our cleaning mechanismindicated generally by the reference character 70 illustrated in FIG. 1includes spaced brackets 74 and 76 carried by a channel iron 72 of theframe of the machine 10. Respective flexible mounting elements 78 on thebrackets 74 and 76 position a tank 80 which rests on a pad 82 of anysuitable shockabsorbing material such, for example, as synthetic rubher,on the channel 72. We provide the tank 80 with an outlet tube 86 theinlet end of which is disposed at a predetermined level above the bottomof the tank 80 so that the tank always contains liquid carrier up tothat level. We also provide the tank with an inlet tube 84 through whichdiluent may be admitted to fill tank 80 to the required level beforebeginning operation of the machine. A bracket 89 in the tank 80 carriesan applicator member such as a sponge 88 adapted to applydeveloperliquid to the cleaner belt in a manner to be described.

A pair of brackets 90 and 92 on the sides of the tank 80 carryrespective bearings .96 and 98 which rotatably receive a shaft 100.Shaft 100 extends through bearings 108 and 109 in the sides 102 and 104of a cleaning belt frame including a center web 106 extending betweensides 102 and 104 and secured thereto by any suitable means such as bywelding. We rotatably mount a second roller shaft 110 on the frame sides102 and 104 at a location remote from the shaft 100. Shafts 100 and 110receive respective belt-supporting rolls 112 and 114 for rotationtherewith and for axial movement relative thereto by means of splines orthe like. Rolls 112 and 114 carry the cleaning belt 116.

A pair of spaced brackets 118 secured to the underside of web 106 carrya guide bar 120 adapted to engage the inner surface of belt 116 to causethe outer surface thereof to conform to the surface of drum 12 over arelatively large area. Another pair of spaced brackets 112 secured tothe underside of the web 106 pivotally carry arms 124 and 126 whichrotatably support a belt tensioning roller 128 adapted to engage theouter surface of the belt 1 16. Springs 130 extending between web 106and the arms 124 and 126 urges roller 128 into engagement with belt 116with sufficient force to give the belt the desired tension. A guide bar131 is supported by the frame in a position to engage the outer surfaceof the outer stand of the belt 116 to increase the area of contactbetween the belt 1 16 and the rollers 112 and 114 to ensure good drivingcontact therebetween. Tank 80 supports a splash shield 133.

A motor 132 supported on the frame side 102 is adapted to be energizedto drive shaft 100 to rotate roll 112. A sprocket wheel 134 carried byshaft 100 at its end remote from motor 132 drives a pitch chain 136which engages a sprocket wheel 138 carried by shaft 110 for rotationtherewith. It will thus be seen that as motor 132 drives shaft 100,rollers 112 and 114 are driven to drive belt 116 by virtue of theirfrictional engagement therewith. We so arrange our system that theportion of the belt 116 in engagement with drum 12 is driven in adirection opposite to the direction of movement of the drum surface.

In the form of our invention illustrated in FIGS. 2 to 5, we reciprocatethe belt 116 transversely of its length as the belt is driven by rollers112 and 114. We form the left edges of the respective rollers with camsurfaces 140 and 142 adapted to engage respective stationary cams 144and 146. Respective compression springs 148 and 150 urge surfaces 140and 142 into engagement with cams 144 and 146. Thus as the rollersrotate they are moved in synchronism back and forth axially so as tocause the belt 116 to reciprocate transversely of its length. Themovement of the belt in a direction opposite to that of the drum surfacetogether with the lateral reciprocation of the belt affords an extremelyeffective scrubbing action on the surface 14 of the drum 12.

Tank 80 rotatably supports a shaft 152 located within the tank adjacentto the top thereof. Shaft 152 carries a wiper blade 154 adapted toengage the outersurface of belt 116 as it emerges from the tank toremove excess liquid therefrom. A spring 158 acts on an arm 156 carriedby shaft 152 at a location outside the tank to urge blade 154 intoengagement with the outer surface of the belt 116.

Referring now to FIG. 6, the cleaning belt, indicated generally by thereference character 116, may be any suitable type which will afford thedesired scrubbing action on the surface 14 of drum 12. One form of beltwhich we have found gives a good scrubbing action is made up of threelayers 160, 162 and 164, of fine, sheer, plain-woven linen cloth such aslawn. These layers may be held together by use of a suitable adhesivesuch as a polyvinyl alcohol glue. Over the layers of lawn we apply alayer 166 of nylon fabric having a pile 168. We adhere the layer 166 tolayer 164. The various layers are assembled on a suitable mandrel andtaped thereon until the adhesive sets. After removal, the

edges are stitched together by means of stitching 170.

We have found that the cleaning action of the belt is enhanced when thesurface 14 is wetted with a liquid developer diluent such as Isopar Gjust before being subjected to the scrubbing action of the. belt. A tank172 holds a supply of the liquid diluent which is fed to a pump assemblyindicated generally by the reference character 176 through a line 174.Pump 176 delivers a metered amount of diluent through a line 178 to amanifold 180. Manifold 180 extends over substantially the entire widthof the drum 12 and is provided with a plurality of spaced outletopenings 182 through which diluent trickles onto the surface 14.

Further to enhance the cleaning action of the belt 116, we mount afloodlight 184 adjacent to the surface of the drum just ahead of themanifold 180. Referring now to FIG. 8, pump 176 includes a housing 186carrying a base plate 188 and provided with a cover plate 190 secured tothe housing by any suitable means such as by screws 192. A recess 194 inthe cover plate 190 is adapted to receive the upper end of a flexiblediaphragm 196. Pump 176 includes a piston 198 secured to the diaphragm196 and adapted to be driven so as to reciprocate the diaphragm with apredetermined stroke.

A motor 200 is adapted to be energized to drive the input of a gear box202 having an output shaft 204 carrying an eccentric 206. The eccentric206 drivingly engages a follower plate 208 on the upper end of the rodof piston 198. An opening 210 in base plate 188 receives an inlet valve212 which admits fluid into housing 186 through a fitting 214 during theupstroke of piston 198. A second opening 216 in base plate 188 receivesan outlet valve 218 which permits liquid to flow out of housing 186through a fitting 220 during the downstroke of the piston 198. It willreadily be appreciated that we connect line 174 to fitting 214 and weconnect fitting 220 to the line 178.

From the structure just described, it will be seen that we have provideda positive displacement pump which delivers the liquid diluent to themanifold 180. We so arrange our system that the amount of diluentsupplied to the surface 14 through the openings 182 is approximatelyequal to the amount of diluent which is lost by evaporation in thecourse of the normal operation of the machine incorporating our cleaningsystem. By way of example we may monitor the level of diluent in tank 52by means of a switch 215 operated by a float 217 to actuate a motorspeed controller 219 of anysuitable type known tothe art to control thespeed of motor 200 and thus the amount of diluent metered onto thesurface 14. We have discovered that the liquid diluent which is lost isfrom approximately 20 to approximately 40 milliliters per hour at acopying speed of about 40 copies per minute. The pump 176 is designed todeliver liquid at a minimum rate of about milliliters per hour. Inresponse to theactuation of the pump piston 198 by the eccentric 206,pump 176 delivers sufficient liquid to the manifold as to maintain thetotal amount of lsopar substantially constant. We achieve this by makingthe holes 182 of such a size that liquid normally is retained in themanifold 180 under surface tension at the holes. When the pump operatespressure of the fluid fed to the manifold overcomes the effect ofsurface tension and drops of liquid fall into the photoconductivesurface 14 across the width of the drum 12. The liquid supplied to thesurface of the drum softens the residual toner to facilitate its removalunder the scrubbing action of the belt 116. The wiper blade 154 removesthe toner and diluent from the surface of the belt to permit it to flowinto the tank 80 from whence it flows through tube 86 back to the supplytank 52. With this arrangement, cleaning of the belt 116 by a servicemanis required at only relatively infrequent intervals.

While the preferred form of our cleaning system incorporates a belt 116which is reciprocated laterally of its length as the belt is driven, inFIG. 9 we have shown a, possible alternate arrangement in which rollers210 and 212 support a belt 214 which may be of the same material as isthe belt 116. Belt 214 has a width which approaches that of the drum l2so as effectively to clean the entire surface thereof. In thisarrangement, as in the case of belt 116, the belt 214 is driven in adirection opposite to the direction of rotation of the drum. In thissystem, the same liquid feeding manifold 180 is used to apply liquiddeveloper to the drum surface as it approaches the cleaning belt. Afterleaving the belt in a manner to be described, the liquid falls into atray 216 from whence it is conducted back to the supply tank 52. In thearrangement illustrated in FIG. 9, a shaft 220 supports a doctor blade218 over the belt so that the blade engages the belt to remove liquidand toner particles from the belt. In order to facilitate passage of theliquid back to the tray 216, we arrange shaft 220 at an angle of about30 to the direction of travel of the belt. An arm 222 carried by shaft220 receives one end of a spring 224 to bias the blade 218 intoengagement with the belt.

As an alternative to the doctor blade arrangement shown in FIG. 9, wemay mount the blade shaft 228 on the tank 216 to-cause the blade 226 toengage the belt 214 at a location at which it is trained around the roll212. A spring 232 acting on an arm 230 on shaft 228 urges the blade intoengagement with belt 214. In this arrangement, liquid collected by theblade 226 is permitted to pass into the tank 216 through a plurality ofholes 234 formed in the blade. A guide portion 236 secured to the edgeof the blade directs liquid back toward the tank 216 thus to prevent itfrom being carried around with the belt. Doctor blades 218 and 226 aswell as guideportion 236 may be made from any suitable relatively rigidmaterial such as brass sheet.

In operation of a copying machine provided with our cleaning system, inorder to make a copy a lamp 18 illuminates surface 14 to afford anexhaust exposure which substantially eliminates any charge remaining onthe drum. Next, the surface passes a corona 20 which applies apredetermined electrostatic charge to the surface. After being charged,the surface is exposed through the machine optics 22 to an image of theoriginal to be copied. The resultant latent image is developed in tank24 with tacky toner particles. After development the surface may againbe exposed to light from a source 26 to overcome the effect of anyresidual background charge. Following that. operation, the image isbrought into contact with paper 28 to which the image is transferred asa result of the fact that the tacky toner particles have greateraffinity for the paper than they do for the photoconductive surface 14.The copy paper carrying the developed image is removed by takeoff rolls38 and 40.

As the surface leaves the takeoff rolls it is first subjected to lightfrom a source 184 to remove any remanent image charge. Any toner depositwhich has not been transferred has a relatively low optical density sothat light from the lamp 184 substantially reduces the charge tofacilitate cleaning. Upon leaving lamp 184, clear liquid carrier isapplied across the surface from the manifold 180 at a rate which isapproximately that at which carrier liquid is lost from the system byevaporation. This clear diluent softens any residual toner deposite onthe drum. Next, the surface passes by the belt 116 which, as is pointedout hereinabove, is driven in a direction opposite to the direction ofmovement of the drum surface. Under the scrubbing action provided by thebelt, the toner particles are removed from the drum and carrieddownwardly toward the tank 80. The wiper blade 154 prevents an excessiveamount of developer from being carried back up to the drum surface.Operation of the forms of belt illustrated in FIGS. 9 and 10 will beapparent from the description hereinabove.

It will be seen that we have accomplished the objects of our invention.We have provided a mechanism for cleaning the photoconductive surface ofan image transfer electrostatic copying machine. Our mechanismeffectively removes any toner deposit remaining on the surface aftertransfer of the image. Our mechanism operates for a relatively longperiod of time without maintenance. It is simple in construction and inoperation for the result achieved thereby.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of ourclaims. It is further obvious that various changes may be made indetails within the scope of our claims without departing from the spiritof our invention. It is, therefore, to be understood that our inventionis not to be limited to the specific details shown and described.

Having thus described our invention, what we claim 1. Anelectrophotographic copying machine including in combination, a memberhaving a photoconductive surface, means for forming a latentelectrostatic image on said surface, a first reservoir for holding asupply of liquid developer comprising tacky toner particles suspended ina carrier liquid, means including said reservoir for developing saidimage with said developer liquid, means holding a supply of copymaterial, means for transferring a developed image from said surface tosaid copy material, a cleaning station, means for moving said membersequentially to carry said surface past said image forming means andsaid developing means and said transferring means and said cleaningstation, an endless belt at said cleaning station in contact with saidsurface, a second reservoir for holding a supply of clear carrierliquid, means independent of said belt for flowing clear developerliquid from said second reservoir onto said surface in advance of itsarrival at said belt, means for driving said belt to remove residualtoner from said surface to which said clear liquid has been applied, andmeans for conducting said liquid which has been flowed onto said surfaceand toner particles removed from said surface by said belt to said firstreservoir.

2. A machine as in claim 1 in which said belt has a rough surface.

3. A machine as in claim 2 in which said member is a drum, said machineincluding means for driving said drum, the surface of said belt engagingsaid drum, and means for driving said belt to move the belt surfaceengaging the drum in a direction opposite to the direction of movementof the drum surface engaged thereby.

4. A machine as in claim 3 in which said cleaning means comprises meansfor constraining said belt to engage said drum over an arcuate area.

5. A machine as in claim 4 in which said belt comprises a pile fabric.

6. A machine as in claim 1 in which said applying means comprises meansfor metering said clear carrier liquid onto said surface at apredetermined rate.

7. A machine as in claim 6 in which said metering means comprises amanifold extending across said surface, said manifold having openingsadjacent to said surface, and means for supplying clear carrier liquidto said manifold.

8. A machine as in claim 7 in which the size of said openings is suchthat carrier liquid normally is held therein by surface tension, saidmanifold supplying means comprising a pump adapted to be actuated toforce liquid into said manifold to overcome said surface tension andmeans for periodically actuating said pump.

9. A machine as in claim 8 in which said pump is a positive displacementpump.

10. An electrophotographic copying machine including in combination, amember having a photoconductive surface, means for producing a latentelectrostatic image extending over an area of said surface, means fordriving said member in a certain direction to move said areasuccessively past a developing station and and an image transfer stationand a cleaning station, a first reservoir for holding a supply of liquiddeveloper comprising tacky toner particles suspended in a diluentliquid, means for maintaining a suspension of said toner particles insaid diluent liquid in said reservoir, means at said developing stationfor applying liquid developer from said first reservoir to said surfaceto develop said image, means at said image transfer station fortransferring the developed image to copy material, an endless cleaningbelt, means mounting said belt at said cleaning station with a portionthereof in engagement with said surface, meansfor driving said endlessbelt to move said portion thereof in a relative direction opposite tothe direction of movement of said member surface, a second reservoir forholding a supply of clear diluent liquid, and means independent of saidbelt and located between said transfer station and said cleaning stationfor flowing clear diluent liquid from said second reservoir onto saidsurface area from which an image has been transferred in advance of thearrival of said area at said cleaning station.

11. A machine as in claim including a source of illumination disposedbetween said transfer station and said cleaning station to reduce theremanent image charge to facilitate cleaning.

12. A machine as in claim 10 including a doctor blade in engagement withthe surface of said belt.

13. A machine as in claim 10 including means for reciprocating said beltin a direction transversely of its length.

14. An electrophotographic copying machine including in combination, amember having a photoconductive surface, means for producing a latentelectrostatic image extending over an area of said surface, means fordriving said member in a certain direction to move said areasuccessively past a developing station and an image transfer station anda cleaning station, means at said developing station for applying liquiddeveloper comprising toner particles and a diluent to said surface todevelop said image, means for holding a supply of said liquid developer,measn for feeding developer from said supply to said developer applyingmeans, means at said image transfer station for tranferring thedeveloped image to copy material, means at said cleaning station forapplying clear diluent to said surface, a cleaning belt, means mountingsaid belt at said cleaning station with a portion thereof in engagementwith said surface, means for driving said belt to move said portionthereof in a direction relatively opposite to the direction of movementof said member surface, means for collecting diluent fed to said surfaceand toner particles removed from said surface at said cleaning stationand means for directing collected diluent and toner to said developersupply.

15. A machine as in claim 14 in which said collecting means comprises atray, a doctor blade and means mounting said blade adjacent to said beltwith the length thereof at an angle to the belt length to cause liquidcollected thereby to flow along the blade toward the tray.

16. A machine as in claim 14 in which said collecting means comprises atray, a doctor blade, means mounting said blade on said tray adjacent tosaid belt, said blade being provided with holes to permit liquidcollected by the blade to pass therethrough, and a guide for directingliquid passing through said holes to said tray.

17. A machine as in claim 14 in which said diluent applying meansapplies diluent to said surface at approximately the rate at which it islost from said machine.

18. A machine as in claim 14 in which said diluent applying meanscomprises a manifold extending across said surface, said manifold beingformed with holes opening toward said surface, the size of said holesbeing such as normally to hold said diluent therein by surface tension,a pump for supplying diluent to said manifold and means for driving saidpump to supply diluent to said manifold to overcome the effect of saidsurface tension.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,776,632 Dated m r 73 Ian E. Smith, Peter J. I-Iastwell and Invent flMarinus C. Vermeulen It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 8, line 35, "'applying' should read flowing Column 9, line 31'measn should read I 5-:- means Signed andaealed this 16th day of April19m.

(SEAL) Attest: v

EDWARD I-I.FLETCHER,JR. C. MARSHALL DANN Attesting ()fficer ICommissioner of Patents FORM P'15 USCOMM-DC 60376-P69 lLS. GOVERNMENTPRINTING OFFICE l9. O-SCG-SS,

UNHED STATES PATENT OFFICE QER'HMCATE @F CORRECTION Patent No. p 632 Datd December 4, 1973 Ian E. Smith, Peter J. Hastwell and Inv n Marlnus c.Vermeulen It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 8, line 35, applying should read flowing Column 9, line 31'measn' should read means Signed and sealed this 16th day of April 19m.

(SEAL) Attest:

EDWARD I'LFLETCHERJR, C. MARSHALL DANN Attesting Officer 7 Commissionerof Patents FORM P0405) ($69) uscoMM-oc 60376-P69 ILS. GOVERNMENTPRINTING OFFICE: l9! 0-366-384,

1. An electrophotographic copying machine including in combination, amember having a photoconductive surface, means for forming a latentelectrostatic image on said surface, a first reservoir for holding asupply of liquid developer comprising tacky toner particles suspended ina carrier liquid, means including said reservoir for developing saidimage with said developer liquid, means holding a supply of copymaterial, means for transferring a developed image from said surface tosaid copy material, a cleaning station, means for moving said membersequentially to carry said surface past said image forming means andsaid developing means and said transferring means and said cleaningstation, an endless belt at said cleaning station in contact with saidsurface, a second reservoir for holding a supply of clear carrierliquid, means independent of said belt for flowing clear developerliquid from said second reservoir onto said surface in advance of itsarrival at said belt, means for driving said belt to remove residualtoner from said surface to which said clear liquid has been applied, andmeans for conducting said liquid which has been flowed onto said surfaceand toner particles removed from said surface by said belt to said firstreservoir.
 2. A machine as in claim 1 in which said belt has a roughsurface.
 3. A machine as in claim 2 in which said member is a drum, saidmachine including means for driving said drum, the surface of said beltengaging said drum, and means for driving said belt to move the beltsurface engaging the drum in a direction opposite to the direction ofmovement of the drum surface engaged thereby.
 4. A machine as in claim 3in which said cleaning means comprises means for constraining said beltto engage said drum over an arcuate area.
 5. A machine as in claim 4 inwhich said belt comprises a pile fabric.
 6. A machine as in claim 1 inwhich said applying means comprises means for metering said clearcarrier liquid onto said surface at a predetermined rate.
 7. A machineas in claim 6 in which said metering means comprises a manifoldextending across said surface, said manifold having openings adjacent tosaid surface, and means for supplying clear carrIer liquid to saidmanifold.
 8. A machine as in claim 7 in which the size of said openingsis such that carrier liquid normally is held therein by surface tension,said manifold supplying means comprising a pump adapted to be actuatedto force liquid into said manifold to overcome said surface tension andmeans for periodically actuating said pump.
 9. A machine as in claim 8in which said pump is a positive displacement pump.
 10. Anelectrophotographic copying machine including in combination, a memberhaving a photoconductive surface, means for producing a latentelectrostatic image extending over an area of said surface, means fordriving said member in a certain direction to move said areasuccessively past a developing station and and an image transfer stationand a cleaning station, a first reservoir for holding a supply of liquiddeveloper comprising tacky toner particles suspended in a diluentliquid, means for maintaining a suspension of said toner particles insaid diluent liquid in said reservoir, means at said developing stationfor applying liquid developer from said first reservoir to said surfaceto develop said image, means at said image transfer station fortransferring the developed image to copy material, an endless cleaningbelt, means mounting said belt at said cleaning station with a portionthereof in engagement with said surface, means for driving said endlessbelt to move said portion thereof in a relative direction opposite tothe direction of movement of said member surface, a second reservoir forholding a supply of clear diluent liquid, and means independent of saidbelt and located between said transfer station and said cleaning stationfor flowing clear diluent liquid from said second reservoir onto saidsurface area from which an image has been transferred in advance of thearrival of said area at said cleaning station.
 11. A machine as in claim10 including a source of illumination disposed between said transferstation and said cleaning station to reduce the remanent image charge tofacilitate cleaning.
 12. A machine as in claim 10 including a doctorblade in engagement with the surface of said belt.
 13. A machine as inclaim 10 including means for reciprocating said belt in a directiontransversely of its length.
 14. An electrophotographic copying machineincluding in combination, a member having a photoconductive surface,means for producing a latent electrostatic image extending over an areaof said surface, means for driving said member in a certain direction tomove said area successively past a developing station and an imagetransfer station and a cleaning station, means at said developingstation for applying liquid developer comprising toner particles and adiluent to said surface to develop said image, means for holding asupply of said liquid developer, measn for feeding developer from saidsupply to said developer applying means, means at said image transferstation for tranferring the developed image to copy material, means atsaid cleaning station for applying clear diluent to said surface, acleaning belt, means mounting said belt at said cleaning station with aportion thereof in engagement with said surface, means for driving saidbelt to move said portion thereof in a direction relatively opposite tothe direction of movement of said member surface, means for collectingdiluent fed to said surface and toner particles removed from saidsurface at said cleaning station and means for directing collecteddiluent and toner to said developer supply.
 15. A machine as in claim 14in which said collecting means comprises a tray, a doctor blade andmeans mounting said blade adjacent to said belt with the length thereofat an angle to the belt length to cause liquid collected thereby to flowalong the blade toward the tray.
 16. A machine as in claim 14 in whichsaid collecting means comprises a tray, a doctor blade, means mountingsaid blade on said tray adjacent to said belt, said blade being providedwith holes to permit liquid collected by the blade to pass therethrough,and a guide for directing liquid passing through said holes to saidtray.
 17. A machine as in claim 14 in which said diluent applying meansapplies diluent to said surface at approximately the rate at which it islost from said machine.
 18. A machine as in claim 14 in which saiddiluent applying means comprises a manifold extending across saidsurface, said manifold being formed with holes opening toward saidsurface, the size of said holes being such as normally to hold saiddiluent therein by surface tension, a pump for supplying diluent to saidmanifold and means for driving said pump to supply diluent to saidmanifold to overcome the effect of said surface tension.